Device for increasing the efficiency of sandblast gun operating by means of compressed air



May 23, 1950 s. MOREL 2,508,766

DEVICE FOR INCREASING TEE EFFICIENCY oF sANDBLAsT GUN OPERATING BY MEANS 0E coMPREssED AIR Filed Dec. 17, 194e Patented May 23, 1950 DEVICE FOR INCREASING THE EFFICIENCY OF SANDBLAST GUN OPERATING BY MEANS OF COMPRESSED AIR Stanislas Morel, Paris, France Application December 17, 1946, Serial No. 716,812 In France January 7, 1946 3 Claims.

It is known that sand-blasting is eiected with an abrasive substance which is projected, cn to the place to be treated, by means of compressed air.

The abrasive substance alone, falling by gravity on to the place to be treated, would be suicient to produce, in time, a satisfactory grinding in m'any cases. The compressed air is added to the abrasive in order to increase the power of the impacts of said abrasive on the place to be treated and accelerate the grinding of the surface. The projection of the mixture of abrasive and compressed air is effected through a nozzle.

It is advantageous to project, in a given time, the largest possible quantity of abrasive with a small amount oi' compressed air, owing to the very high cost of compressing air. Unfortunately, in the known sand-blasting devices, it is impossible to exceed a certain percentage of abrasive relatively to the quantity of air since, if the abrasive is too dense in the pipe and in the nozzle, the speed of the air and sand mixture is slowed down which considerably impairs the efficiency.

As it is impossible to increase the rate of discharge of abrasive without increasing the consumption of compressed air, it is necessary, in order to increase the power of the sand-blast, to give a larger cross-section to the pipe and to the nozzle, but the eicacy is not increased thereby and the costs increase in proportion to the power of the sand-blast.

The present invention has for its object to provide a device which can be fitted to all sandblasting installations operating by means of compressed air and which enables the eicacy to be increased by increasing the rate of discharge of abrasive without involving an additional consumption of compressed air, thereby very substantially lowering the cost of the sand-blasting operation.

The device may operate in several ways, according to whether the` sand-blast installation operates by pressure or by suction.

In all cases, the mixture of compressed air and abrasive, which ows out of the nozzle of said gun installation into the rear end of the discharge nozzle xed to the front of the body of frusto-conical or like shape, causes an additional quantity of abrasive to be sucked through the aforesaid tube or tubes and this abrasive enriches the mixture projected through said discharge nozzle on to the parts to be sand-blasted.

In the accompanying drawing, which is given solely by way of example:

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Fig. l is a longitudinal section of a, device according to the invention, in the case of a sandblast apparatus operating by pressure;

Fig. 2 is an elevational view thereof;

Fig. 3 is a view on a smaller scale in the case of a suction operated sand-blast gun.

According to the embodiment shown in Figs. 1 and 2, the device according to the invention comprises a frusto-conical body I, on the small base of which is xed, by means of a screwed nut 2, a tubulure or discharge nozzle 3 intended for the outlet of the final mixture of abrasive and compressed air. Preferably, this tubulure or nozzle is made of a very strong metal or alloy, for example of tungsten steel.

On the large base side opposite, the cone frustum l' is closed by means of a screwed head 4. Said head is provided at its centre and on its rear face with a cylindrical boss 5 having therein like the head a tapped hole 5. In said hole 6 is screwed a nozzle-holder 1 xed in position by means for example of a screw 8. In said nozzleholder l is screwed the neck 9 of the usual nozzle i6 of an usual sand-blast apparatus. The neck 9 and the nozzle Il) are made of tungsten steel or other strong metal or alloy. The nozzle I0 is locked in position for example by means of one or a plurality of screws Il. Its normal length is such that its free front end a is adjacent the flared rear end l2 of the discharge nozzle 3, the diameter d1 of which is larger than the diameter d2 of the nozzle l0.

Towards the rear a sleeve i3 connects to the bess 5 a tube li on which is fixed a pipe l5 which is preferably flexible, made of rubber for example, and which is intended for the supply of a usual mixture of abrasive and compressed air.

On either side of the boss 5, the head 4 carries two tubes IS which are preferably arranged obliquely with respect to the longitudinal axis XX of the device so as to converge towards the flared mouth l2 of the tubulure 3. To eachof the tubes I6 is connected a pliable or exible tube l1 for the supply of additional abrasive.

Preferably, one or more collars I8 secure said tubes il to the main tube l5.

Before explaining the operation of the device, it will be pointed out that this device, which comprises the body l the tubulure 3, the head 4 with its tubes i6, is merely added to a pressure sandblast apparatus comprising the nozzle-holder l, the nozzle neck 9 and the nozzle I0, which are supplied with a mixture of abrasive and pressure air through the pipe l5.

The device operates as follows:

sive of a normal pressure sand-blast apparatus issues powerfully in the form of a jet f1 from the nozzle I and flows out through the discharge nozzle 3 on to the place to be treated.

If the pipes Il are connected to distributors which are xed to a hopper or dip in a receptacle containing abrasive, additional abrasive isdrawn into said pipes and into the tubes I6 by the stream of atmospheric air which is produced owing to the ra-refaction of the air produced in the nozzle 3 and the body I by the main jet ,f1 of abrasive and compressed air issuing from the nozzle I0. In this case. the device according to the invention enables a substantial increase of efiiciency to be obtained, since the additional abrasive thus drawn in without its being necessary to increase the quantity of compressed air flows in the direction of the arrows f2 and mixes with the jet f1, thereby considerably enriching it with abrasive.

If, on the other hand, the tubes Il are connected to a reservoir with a head of abrasive (sand-blast machine), a stream of abrasive is driven into said tubes simultaneously by the pressure exerted in said reservoir and by the vacuum in the body I. The additional abrasive is forced into the cone fr'ustum l, then iiows into the tubulure 3 and 'iss-ues therefrom mixed with the compressed air "and the abrasive supplied by the nozzle l0 as in the previous case.

Fig, 3 shows the device in position on an ordinary suction operated sand-blast gun. In this case, the device is fixed by its head @l on the nozzle Il! of the gun, which operates by means of 'a supply oi compressed air through. the pipe 2l. This air sucks the abrasive, which is fed through a nipple 2U, into the body i9. The mixture of abrasive and compressed air flows through the nozzle or injector tube lil into the discharge nozzle 3 like the mixture oi' abrasive and compressed air of the previous example and the eiiect is the same. The eiiiciency of the sand-blast gun is likewise increased, but to a smaller extent than with a pressure operated sand-blast machine, owing to the fact that there is a substantial loss or" pressure of the compressed air in the actual nozzle of the gun.

Naturally, the invention is in no way limited to the embodiments illustrated and described, which have only been chosen by way of example.

Having now described my invention, what I 'claim new and desire to secure by Letters Patent is:

1. In combination with a sand-blast gun having an outlet nozzle connected with a source oi compressed air and means for suspending abrasive particles 4in the stream of compressed air flowing through said nozzle, an attachment adapted to increase the abrasive power of said gun, said attachment comprising an injector casing generally of trapezoidal longitudinal section tapering toward a front outlet oriiice, a cylindrical discharge nozzle fitted in said orii'lce in the longitudinal axis of said casing, the rear end of the inner wall of said discharge nozzle substantially merging with the inner wall of said casing, whereby the path of any abrasive particle moving in contact with the inner wall of said casing and of said nozzle from the rear of said casing to the discharge end of said nozzle is unobstructed, an injector tube, means for connecting the rear end of said injector tube with the outlet nozzle of said sand-blast gun, said. injector tube being secured to the rear face of .said casing and extending along the axis thereof close to the inlet end of said discharge nozzle, whereby a suction effect is produced in said casing and at least one abrasive material feeding pipe opening in said casing in a direction substantially parallel with the lateral inner wall of said casing and such that the rectilinear path of any abrasive particle discharged from said pipe under the sucking effect produced therein is unobstructed by said injector tube.

2. In combination with a sandblast gun having an outlet nozzle connected with. a source of compressed air and means for suspending abran sive particles in the stream of compressed air iiowing through said nozzle, an attachment adapted to increase the abrasive power of said gun, said attachment comprising an injector casing generally of trapezodal longitudinal section tapering toward a front outlet orice, a cyline drical discharge nozzle fitted in said orifice in the longitudinal axis of said casing, the rear end of the inner wall of said discharge nozzle substantially merging with the inner wall of said casing, whereby the path of any abrasive particle moving in contact with the inner wall of said casing and of said nozzle from the rear of said casing to the discharge end of said nozzle is unobstructed, means for securing to the rear face of said casing the outlet nozzle of said sand-blast gun, said outlet nozzle extending along the axis of said casing close to the inlet end of said discharge nozzle, whereby a suction ciiect is produced in. said casing and at least one abrasive material feeding pipe opening in said casing in a direction substantially parallel with the lateral inner wall. of said casing and such that the rectilinear path of any abrasive particle discharged from said pipe under the sucking eiiect produced therein is unobstructed by said outlet nozzle of said sand-blast gun.

3. A sand blasting process comprising projecting a stream of compressed air having in suspension therein the maximum amount of abrasive particles compatible with the rate of flow of the stream into a chamber having a discharge opening, feeding additional abrasive particles into said chamber at a point immediately ahead of the discharge opening and discharging from the opening a stream of abrasive particles and air in which the amount of abrasive particles substantially cxceeds the maximum amount compatible with the rate of flow of the compressed air stream discharged into the chamber.

STANISLAS MOREL.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 821,415 Hess May 22, e` 1,107,244 Carter Aug. l1, 1914 1,605,617 Ruemelin Nov. 2, 1926 FOREIGN PATENTS Number Country Date 1,510 Great Britain Jan. 20, 1910 

